1. Technical Field
The present invention relates to a selection device, and more particularly, to a selection device for non-volatile memory.
2. Description of the Related Art
Recently, a resistive random access memory (RRAM), which is a non-volatile memory, has attracted attention due to its various advantages, such as simple structure, low power consumption, high integrity, excellent availability, rapid switching rate, and the like.
In particular, a bipolar RRAM has excellent switching uniformity and memory characteristics and thus has been actively investigated.
Recently, a cross-point array structure has been broadly used to realize high integration of a resistive random access memory. In the cross-point array structure, word lines and bit lines are formed to cross at a right angle and a resistive random access memory cell is disposed at each cross point therebetween. However, the cross-point array structure can suffer from current leakage such as sneak path current through an adjacent memory cell which is not selected. The sneak path current generates interference in a reading operation, thereby causing misreading and increase in power consumption. As a technique for suppressing current leakage such as sneak path current, a selection device has been suggested. First, as a selection device, use of a diode such as a p-n junction diode, a Schottky diode, and the like was proposed. However, the diode-based selection device allows a significantly low current to pass through the diode in a reverse-bias state, and thus cannot be used as the selection device in a bipolar resistive random access memory.
In addition, a Ni/TiO2/Ni structure including an oxide monolayer was proposed as the selection device. However, the oxide monolayer selection device has a low on-current density of about 105 A/cm2, thereby making it difficult to record data on the resistive random access memory.